In the prior art, suspension systems providing bidirectional restraint to a linear actuator have usually included a pair of helical compression springs located one on each side of the shaft or force motor. As a result, adjustment of the apparatus becomes extremely difficult and, in addition, overall length of the device may be excessive, precluding its utilization under many circumstances.
In addition to the utilization of a plurality of compression springs the best prior art known to applicants includes U.S. Pat. Nos. 2,169,850, 2,337,902 and 2,942,459.